Means for transferring corrosive liquids



Jan. 19, 1960 I D. A. LIPPS 2,921,600

MEANS FOR TRANSFERRING CORROSIVE LIQUIDS Filed March 19, 1957 2 Sheets-Sheet 1 INVENTOR DELBERTAUPPS Jan. 19, 1960 D. A. LIPPS 2,921,600

MEANS FOR TRANSFERRING CORROSIVE LIQUIDS Filed March 19, 1957 2 Sheets-Sheet 2 WVQK INVENTOR DELBERT ALIPPS United States Patent MEANS FOR TRANSFERRING CORROSIVE LIQUIDS Delbert A. Lipps, New Orleans, La., assignor to Freeport Sulphur Company, New York, N. Y., a corporation of Delaware Application March 19, 1957, Serial No. 647,045

9 Claims. (Cl. 137-340) This invention relates to pipe connection constructions for transferring corrosive liquids from sources of supply to autoclaves for injection therein under pressure. More particularly, it relates to pipe and coupling arrangements for the injection of concenetrated sulfuric acid into autoclaves containing aqueous treating or leaching liquids operating at high temperatures and pressures.

In the leaching of nickeliferous iron ores with dilute sulfuric acid utilizing high temperatures (up to 475 F.) and pressures (up to 520 p.s.i.g.), it is recognized that corrosion properties are lessened by storing and transferring the sulfuric acid in concentrated form to the high pressure leaching vessel containing the finely divided ore in aqueous slurry form, the dilution of the acid to the desired strength occurring in the vessel. Although acid resistant metal pipes for transferring and injecting the acid will successfully withstand corrosion by the concentrated acid, unavoidable contact between the injection pipe and acid in a range of dilutions occurs. If the injection pipe terminates in the vapor space of the autoclave, the dilution will occure at the discharge tip of the pipe as a result of the combination of condensing steam with the acid. Also when the introduction of the acid is discontinued, the acid will flow out of the pipe, and steam will flow back up into the pipe, condense and dilute the acid, there corroding the inside of the pipe, back to the check point, i.e. a valve, a check valve or a liquid seal. If the acid injection pipe terminates below the surface of the aqueous slurry, corrosion at the pipe terminus and within the pipe likewise unavoidably occurs.

To overcome this corrosion problem, a number of steps have been tried without adequate success. Glass lined piping was tried and it resisted the corrosion, but breaking was unavoidable due to vibration of the autoclave and connections thereto. Tetrafluoroethylene (Teflon) tubes placed within metal tubes also resisted corrosion but they were only partially successful because the plastic expands excessively on heating and is subject to deformation under the heat and physical pressure encountered, thus permitting leaks to develop at the point of junction with the metal pipe leading from the concentrated acid source.

An object of the present invention is to provide an injection pipe and connection which overcomes all of the hereinbefore mentioned limitations and which provides for continual operation of the autoclave processing over long periods of time without interruption due to corrosion, breakage or other faults.

Broadly considered, the invention may be defined as involving an injection line and connecting construction for intermittently feeding or transferring concentrated, or relatively concentrated sulfuric acid or other corrosive liquid from a storage tank or other source to an autoclave which comprises a plastic tube resistant to corrosion by such corrosive liquid at all concentrations or dilutions, having one end terminating within or a a wall of the autoclave and the other in one side of a coupling the other side of which coupling is connected to a source 7 2,921,600 Patented Jan. 19,1960- any diluted liquid from flowing back to the coupling where it would cause corrosion.

The plastice pipe is preferably constructed of tetra-- fluoroethylene, for it will withstand all concentrations of sulfuric acid at all temperatures which will be encoun-- tered, i.e. from room temperature up to 475 F. Its high coefiicient of expansion and deformation characteristics under these changing temperature conditions are eliminated as a consideration by the manner of connecting the tube into the autoclave and the cooling effect obtainable in the pipe leading to the coupling. Other corrosion-resistant plastic tubes contemplated are fabricated from other halogen carbon resin compounds related to tetrafluoroethylene, from silicone resins or from various tough phenolic resins.

When the plastic tube is in its preferred form, an inverted U loop, a column of concentrated acid or other liquid is always retained in the leg of the tube starting'at and leading from the coupling where the plastic tube is joined to the metal pipe leading to the liquid source. Thus the steam and excessive heat of the autoclave is prevented from reaching the coupling. The coupling between the plastic tube and liquor source is accomplished through the use of a liquid-tight friction joint.

The inability of the plastic tube to withstand the vapor pressure under which the autoclave is operated is over come not only by the provision of the surrounding metal pipe or armour pipe but also by the arrangement of the end of the tube and the pipe in the autoclave. The annulus or area between the tube and pipe is left open to the pressure within the autoclave and hence the pressure on the outside of the plastic tube is the same as that on its inside surface, excepting of course, the slightly greater pressure created inside the tube during the introduction of the acid. The armour pipe should have heat radiating surfaces adequate to prevent heat from the autoclave from damaging the plastic tube connection at the coupling. Such radiation may be provided by the length of the armour pipe exposed to the atmosphere or by a cooling means applied to the pipe.

The looped tube and pipe, or at least the top portions thereof, are preferably arranged above the level of the autoclave and connect into the top thereof or into the vapor space above the liquid reaction mass. The plastic tube may terminate in the upper part or vapor space or in the lower part or below the liquid level. The armor pipe likewise may terminate at any level or at the autoclave wall, but it should have one or more openings into the vapor space to prevent the acidic-reaction liquid from backing up into the annulus between the plastic pipe and the armour pipe where corrosion would occur. When the armour pipe projects into the acidic reaction mass, it can be fabricated of titanium metal. In all of these arrangements, the plastic tube advantageously is longer than the armour metal pipe, thus providing a free end of the plastic tube.

The invention may be more completely understood 3 plastic tube and surrounding pipe to the acid-supplying metal pipe. Figures 3 and 4are diagrammatic elevations of connecting lines of alternative configurations.

With reference to Figure 1 there is illustrated an autoclave from which all conventional inlets, outlets, stirring equipment, heating devices and controls, not a part. of the :presentinvention have been eliminated. The autoclave has an acid injecting line connecting into the top thereof'composed of a plastic tube 11 (M /1D. x 2 2" OD. nominal) and a surrounding protective stainless steel .pipe 12 /2"), the pipe being welded to a flange 13' in turn attached to the top of the autoclave 10. The metal'pipe is concentric withthe plastic tube and contacts the same to provide the needed strength.

Within the autoclave 1.0, the metal pipe is connected through a union 14 to a titanium .pipe 15, preferably of somewhat larger interior diameter than the exterior diameter of the tube, terminating below the operating liquid level in the autoclave. This titanium pipe has one or more holes 16 near its upper :end, at a level opening into the operating vapor space.

The plastic tube 11 and armour pipe 12 extend upwardly from the autoclave 10 and provide a loop, suitably of a twelveinchradius. The other end of the loop terminates in a coupling 17 in which the plastic tube is'held in part byfriction to the apertured member 18 having a tapered projection 19 which extends upwardly within the plastic tube, the base section of the member 18 being screwed into the center flange 22. The pipe 12 is welded to the flange 21 and the flange 23 to the pipe 24 leading to an acid storage tank from which the acid can be forced under pressure. The three flanges are clamped or bolted together and have gaskets 25 of acid resistant material therebetween, suitably of thesame plastic as the tube 11.

The tube 11 and pipe 12 may have any configuration which provides an upwardly extending section leading from the coupling 17 to the autoclave 10. With this construction, a body of concentrated acid is always maintained in this section of the tube 11. When the pumping of .acid into the autoclave is discontinued, concentrated acid'in the tube-11 willflow therefrom into .the autoclave only from a point A, the acid being replaced by steam which, in part, will condense and flow back into the autoclave. Hence no diluted acid will flow to the coupling or into the acid supply pipe toattack the metalandcause leakage.

.In constructions tested to date, the plastic tubesll and pipes 12 have been long enough to dissipate heat from the autoclave in amounts adequate for preventing the tube from swelling, contracting and deforming to an extent endangering the tight junction of the plastic tube with the coupling 17. Although the loop-configuration itself may be considered a means for dissipating excessive heat, it is recognized that an additional coolingmeans may be required, as when the connecting pipe is made very short. A cooling jacket or other heat dissipating means (not shown) may be mounted on the pipe '12 adjacent the coupling 17 With reference to Figure 3, an alternative connecting pipe is illustrated having an upwardly extending section which will maintain corrosive liquid in the tube when the feeding of liquid is discontinued. In Figure 4, substantially the whole of the tube and pipe extends upwardly in connecting the coupling with the autoclave, and again a concentrated liquid barrier will be maintained in the tube for the portection of the coupling metal. This relatively short pipe is, provided with a cooling jacket 26 which will prevent heat at the very high temperatures employed in the autoclave from reaching the coupling17 and destroying the leak-proof junction of the plastic tube with the metal .pipe.24 leading from the acid supply tank.

Although the construction .hereinbefore described is particularly applicable to processessutilizing sulfuric acid, it is also applicable with substantial advantage to other processes and systems utilizing liquids corIQSiveto con- 4 ventional' construction metals at intermediate or reduced dilutions, as strong caustic alkalies and various organic intermediates.

It should be understood that the instant invention is not limited to the specific procedures or conditions herein described but that it extends to all equivalents which will occur to those skilled in the art'upon consideration of the scope of the claims appended hereto.

I claim:

1. A corrosion-resistant injection line and connecting structure which comprises a plastic tube resistant to the liquid to be injected having one end terminating within an autoclave to which the liquid is to be injected and the other in a coupling the other side of which coupling is connected to a supply source of said liquid, a metal pipe concentrically surrounding and contacting said plastic tube attached to the autoclave and having an opening into the vapor space in the top' part of the autoclave and attached at its other end to said coupling, said tube and pipe at least impart extending upwardly from the coupling to the autoclave, whereby the corrosive liquid will remain in at least part of the tube by the force of gravity when the feeding of corrosive liquid has been stopped.

2. The injection line and connecting construction of claim 1 whereinthe metal pipe connecting said coupling to said autoclave is provided with a-cooling means.

3. -An injection line and connecting construction for intermittently feeding concentrated corrosive liquids from a supply source to an autoclave which comprises a plastic tube resistant to corrosion by such liquid under all concentrations having one end terminating within the autoclave and the other in one side of a coupling the other side of which coupling is connected to a supply line for said liquid, a corrodible metal pipe concentrically surrounding and contacting said plastic tube attached at one end to said autoclave and having an opening into the vapor space in the top part of the autoclave and attached at the other end to said coupling, the portion of the plastic tube extending .into the autoclave being longer than that of the corresponding portion of the metal pipe, said tube andpipe at least in part extending upwardly from the coupling to the autoclave, whereby the corrosive liquid will remain in at least part of the tube by the force of gravity when the feeding of corrosive liquid has been stopped.

4. The injection line and connecting construction of claim 1 wherein said tube and pipe have a section in the form of an upwardly extending loop.

5. An injection line and connecting construction for intermittently transferring concentrated corrosive liquids from a storage tank to an autoclave which comprises a plastic tube resistant to corrosion by such liquid under all dilutions having an end terminating in a lower zone below'the operating liquid level insaid autoclave and the other in one side of a-coupling the other side of which coupling is connected to a supply line for said liquid, a metal pipe concentrically surrounding and contacting said plastic tube attached at one end to a wall of said autoclave and also terminating in said lower zone, said pipe having an opening in the side thereof at a level in an upper or vapor zone of said autoclave, the other end of said pipe being attached to said coupling, said tube and pipe'at least in part extending upwardly from the coupling :to the autoclave, whereby the corrosive liquid will remain in at least part of the tube by the force of gravity when the feeding of corrosive liquid has been stopped.

6. Aninjection line and connecting construction for intermittently "transferring concentrated corrosive liquids from a storage tank to an autoclave which comprises a tctrafluoroethylene tube having one end extending into the top of said autoclave 'and'the other in one side of a'coupling the other side of which coupling is connected to a supply line for said liquid, a metal pipe concentrically surrounding and 'contactingsaid plastic tube attached "at one end to said autoclave and having an opening into the vapor space in the top part of the autoclave and at the other end to said coupling, said tube and pipe having a section thereof in the form of an inverted U.

7. The injection line and connecting construction of claim 1 wherein said tube is composed of tetrafluoroethylene.

8. An injection line and connecting construction for intermittently transferring concentrated corrosive liquids from a storage tank to an autoclave which comprises a plastic tube resistant to corrosion by such liquid at all concentrations having one end terminating within the autoclave and the other in one side of a coupling the other side of which coupling is connected to a supply line for said liquid, a metal pipe concentrically surrounding and contacting said plastic tube attached at one end to said autoclave and having an opening into the vapor space in the top part of the autoclave and at the other end to said coupling said pipe having radiating surfaces suflicient to prevent heat damage in the coupling, said tube and pipe at least in part extending upwardly from References Cited in the file of this patent UNITED STATES PATENTS 931,647 Rademacher Aug. 17, 1909 1,461,520 Forman July 10, 1923 1,528,822 Gilchrist Mar. 10, 1925 1,607,801 Nichols Nov. 23, 1926 1,783,163 Griswold Nov. 25, 1930 2,088,922 Porteous Aug. 3, 1937 2,723,882 Barnett Nov. 15, 1955 FOREIGN PATENTS 1,052,048 France Sept. 23, 1953 

